The present invention relates to the production of siloxane-polyoxyalkylene copolymers, referred to herein as xe2x80x9cCopolymersxe2x80x9d.
The use of platinum catalysts for the addition of silanes or siloxanes with SiH groups to compounds with one or more olefinic double bonds, a reaction commonly referred to as hydrosilation or hydrosilylation, is well known. The addition reaction, however, proceeds without an appreciable formation of by-products, only if the compounds that have the olefinic double bond are free of groups which can react with the SiH group in competition with the addition reaction. This includes particularly the carbon-linked hydroxyl group. In practice it frequently happens that the hydrosiloxanes or hydrosilanes must be added to compounds with olefinic unsaturations, which also have hydroxyl groups or other reactive groups. An example of such a reaction is the addition of hydrosiloxane to an unsaturated alcohol or polyether. There is thus, a need for an economical process which, on one the hand, has a high activity to the addition of the SiH group to the olefinic double bond, and on the other hand, minimizes the side reactions.
Besides the aforementioned competing reaction in the form of the reaction of the SiH and COH groups, it is desired to also avoid disproportionation reactions within the silane or siloxane compounds. Such disproportionation reactions are understood to include a redistribution of the SiH groups, which are usually present in the mixture of silanes or siloxanes. Further side reactions or secondary reactions are the conversion of the allyl groups to propenyl groups, or the possible crosslinking of the addition compound that has terminal OH groups, via acetal formation with the propenyl ether groups. Both reactions generally are catalyzed by chloroplatinic acid (H2PtCl6.6H2O), and lead, on the one hand, to an inadequate conversion of the SiH groups and on the other hand, to an increase in viscosity of the end product.
The introduction of carboxylate salts of alkali and alkali earth metalsxe2x80x94sodium propionate in particularxe2x80x94and solventless processing, have significantly improved the efficiency of copolymer production, as well as drastically cut batch cycle times. The use of sodium propionate often leads to the need for multiple catalysis or requirements of greater initial catalyst charge. Consistent with a longer induction period is greater selectivity to copolymers that are of the higher molecular weight analogs, which often give lower cloud points and reduced water solubility. Sodium propionate for the most part, is relatively insoluble in the reactants as well as the generated copolymers, and must be removed by post hydrosilation filtration. Sodium propionate in the presence of water, catalyzes dehydrocondensation potentially liberating hydrogen gas.
The use of sodium phosphate salts as buffers in solventless processes, have shown some improvement over sodium propionate. There is no detected inhibition in the rates of hydrosilation, and the resulting copolymers give water solubility and cloud points, that are comparable to those given by copolymers made in toluene. Sodium phosphate salts however, are very polar and dense, thus are hard to disperse throughout the reactant mixture. Settling is prone to occur, which severely limits their effectiveness.
U.S. Pat. No. 4,847,398 describes a process for the preparation of siloxane-oxyalkylene copolymers via a solventless hydrosilation in the presence of carboxylic acid salts. Although side reactions such as dehydrocondensation and acetal formation were much reduced by the use of these carboxylic acid salts, the rates of the hydrosilation reactions were somewhat inhibited, with the resulting Copolymers consisting of higher molecular weight analogs. This is evident in the relatively lower water solubilities that are characteristics of these copolymers.
U.S. Pat. No. 5,191,103 teaches the use of sterically hindered, nitrogen-containing and phosphorus-containing compounds as buffer-catalyst modifiers in the preparation of Copolymers. These amines and phosphines work to reduce dehydrocondensation and acetal formation and are often solids or high boiling liquids, which must either be removed by post hydrosilation filtration, or be allowed to remain in the resulting copolymer. As these compounds may be basic and cannot be removed by stripping, post hydrosilation neutralization is necessary in order to obtain a pH neutral copolymer. This need for additional processing lengthens the overall batch cycle time of the copolymer production, particularly where the buffer-catalyst modifier is solid, and limits their utilization in cosmetics and personal care applications, where the buffer-catalyst modifier is a high boiling liquid.
Separately, U.S. Pat. No. 4,292,434 teaches the use of a platinum catalyst that is specially modified, firstly by reaction with an olefin, and further with a primary or secondary amine. The need for pre-formation of the catalyst complex, prior to the hydrosilation, adds much additional expense, as well as lengthening the process time for the copolymer. Moreover, the catalyst package is more ideally suited for reactions involving monomeric or dimeric silicon compounds as opposed to polymeric silicones of the present invention.
This invention disclosure describes an improved process for the preparation of Copolymers via a solventless hydrosilation of oxyethylene-rich polyethers in the presence of an ether, hydroxy or carbonyl modified amine as a buffer-catalyst modifier. The common side reactions such as dehydrocondensation and acetal formation are significantly reduced or eliminated, by the use of these amines. Undesirable side reactions such as acetal formations and dehydrocondensation are reduced or eliminated, when these amines are combined with the reactants. They are liquids at ambient temperature with boiling points ranging from 70xc2x0 C. to 220xc2x0 C. They are also completely miscible with the polyether-siloxane fluid admixture, thus are easily dispersed, without the risk of sedimentation. Rates of hydrosilation are minimally or not at all affected by these amines, thus there is virtually no induction period, and the resulting copolymers give comparable water solubility characteristics to those made in solvents. Since the amines have relatively low boiling points, optional removal by post hydrosilation stripping is possible, for Copolymers whose end-use is in cosmetics and or personal care applications. These amines unlike sodium propionate, do not catalyze the undesirable dehydrocondensation side reaction. When amines of the invention, are utilized, reduced levels of noble metal catalyst are possible during the hydrosilation, and the resulting copolymers possess water solubility characteristics that are equivalent to those of Copolymers prepared in solvent.
The present invention is directed to an improved process for the preparation of Copolymers, and to products obtained by this process. These Copolymers are prepared by a hydrosilation reaction between (i) an organohydrogen-polysiloxane and (ii) at least one unsaturated polyoxyalkylene, in the presence of (iii) a modifier, which is a primary, secondary or tertiary amine with an alkyl group having a hydroxyl, ether, or carbonyl functionality and a boiling point below 220xc2x0 C., preferably between 70xc2x0 C. and 200xc2x0 C., and more preferably 95xc2x0 C. to 180xc2x0 C. and (iv) a noble metal hydrosilation catalyst. The amine is believed to act as a buffer-catalyst modifier. The reaction is carried out in the presence of, or more preferably, in the absence of a solvent. Benefits include the elimination of need for post hydrosilation pH adjustments and filtration and extended solvent stripping, as well as improved per batch yields and significant reduction in batch cycle times. Reduced noble metal catalyst usage and the production of Copolymers that consistently give improved water solubility are achieved. A wider utilization of these copolymers in cosmetic, personal care and textile applications is another benefit, as well as the production of Copolymers that exhibit reduced polydispersity in their molecular weight distributions, i.e., relative to the product made without such an amine a decrease of at least 45% in Mw/Mn polydispersity ratio (as measured by gel permeation chromatography(gpc)). Tighter molecular weight distributions will also provide benefits in applications such as polyurethane foam, coatings, agricultural formulations and antifoam compositions.
A preferred embodiment of the process is as follows:
1). forming a mixture of:
(i) an organohydrogensiloxane having the unit formula: [RaHbSiO(4-a-b)/2]n wherein R denotes a monovalent hydrocarbon radical free of aliphatic unsaturation and has 1 to 8 carbon atoms, a has an average value of 1 to 3, b has an average value of 0.01 to 1.5, the sum of a+b has an average value of 1 to 3, and n denotes the number of siloxane units, having a value of 2 to 200, and
(ii) at least one polyoxyalkylene having the average formula
R1(OCH2CH2)z(OCH2 [R3] CH)wxe2x80x94OR2 or 
R2O(CH[R3]CH2O)w(CH2CH2O)zxe2x80x94CR42xe2x80x94Cxe2x89xa1Cxe2x80x94CR42xe2x80x94(OCH2CH2)z(OCH2[R3]CH)wOR2 
wherein R1 denotes an aliphatically unsaturated hydrocarbon group containing from 2 to 10 carbon atoms, R2 is R1, hydrogen, an alkyl group containing 1 to 8 carbon atoms, an acyl group containing 2 to 8 carbon atoms, or a trialkylsilyl group. R3 is a monovalent hydrocarbon group containing 1 to 18 carbon atoms. R4 is R3 or hydrogen, z has a value of 0 to 100 and w has a value of 0 to 80, and
(iii) at least one amine having an alkyl group with hydroxyl, carbonyl, or ether functionality, which has a boiling point below 220xc2x0 C. at atmospheric pressure, and
2) adjusting and maintaining the temperature of the mixture to promote the reaction of the organohydrogensiloxane with the polyoxyalkylene, and
3). providing to said mixture, a catalytically effective amount of a noble metal hydrosilation catalyst, and
4). maintaining the temperature of said mixture below 120xc2x0 C. to reaction completion, and
5). recovering said copolymer.
Undesirable side reactions such as acetal formation and dehydrocondensation are reduced or eliminated, when these amines are utilized in the hydrosilations. The amines are liquids and are very miscible with the polyether-siloxane premix, thus are easily dispersed, without the risk of sedimentation. They have relatively low boiling points, thus are removable from the copolymer after the hydrosilation is completed. Since the amines have relatively low boiling points, optional removal by post hydrosilation stripping is possible, for copolymers whose end use is in cosmetics and or personal care applications.
The term xe2x80x9csolventlessxe2x80x9d means that no added solvent, volatile or otherwise, is employed in the hydrosilation reaction of the organohydrosiloxane and the polyoxyalkylene. Any small amount of other liquids which might be introduced with, for example, the catalyst, is incidental and is not considered to be a reaction solvent.
Organohydrosiloxanes
Organohydrogensiloxane compounds useful in the present invention for the preparation of the surfactants include those represented by the formula:
[RaHbSiO(4-a-b)/2]n 
wherein R denotes a monovalent hydrocarbon radical free of aliphatic unsaturation and has 1 to 8 carbon atoms, a has an average value of 1 to 3, b has an average value of 0.01 to 1.5, the sum of a+b has an average value of 1 to 3, and n denotes the number of siloxane units, having a value of 2 to 200.
The organohydrogensiloxane can contain any combination of siloxane units selected from the group consisting of R3SiO1/2, R2HSiO1/2, R2SiO2/2 RHSiO2/2, RH2SiO1/2, RSiO3/2, HSiO3/2 and SiO4/2 provided that the organohydrogensiloxane contains sufficient R-containing siloxane to provide from 1 to 3 R radicals per silicon atom and sufficient H-containing siloxane units to provide from 0.01 to 1.5 silicon-bonded hydrogen atoms per silicon and a total of R radicals and silicon-bonded hydrogen atoms of from 1 to 3 per silicon.
The preparation of organohydrosiloxanes is well known, and is set forth, for example, in The Chemistry and Technology of Silicones, Noll W., Academic Press (New York): 1968, Chapter 5 p. 191-246. Illustrative of suitable radicals are alkyl radicals such as methyl, ethyl, propyl, butyl, tolyl, xylyl, and substituted hydrocarbons groups such as heptafluoropropyl. R is preferably methyl.
Polyethers
Unsaturated polyoxyalkylene reactants, which can be employed in the process of this invention, include those having the formula:
R1(OCH2CH2)z(OCH2[R3]CH)wxe2x80x94OR2, or 
R2O(CH[R3]CH2)w(CH2CH2O)zxe2x80x94CR42xe2x80x94Cxe2x89xa1CCR42xe2x80x94(OCH2CH2)z(OCH2[R3]CH)wOR2 
wherein R1 denotes an unsaturated organic group containing from 2 to 10 carbon atoms such as vinyl, allyl, methallyl, propargyl or pentynyl. When the unsaturation is olefinic, it is desirably terminal to facilitate complete hydrosilation. R2 is R1, hydrogen, an alkyl group containing 1 to 8 carbon atoms, an acyl group containing from 2 to 8 carbon atoms, or a trialkylsilyl group. R3 and R4 are monovalent hydrocarbon groups containing 1 to 18 carbon atoms. R4 may also be hydrogen. Methyl is the most preferred R3 group. Z has a value of 0 to 100 and w has a value of 0 to 80. Preferred values of z and w are 1 to 50 inclusive. The unsaturated polyether, whether comprised of alkyne groups or terminal olefinic groups, may be a blocked or a randomly distributed copolymer of differing oxyalkylene units.
Amines
The buffer-catalyst modifier is a a relatively volatile liquid amine, which allows for easy removal by post hydrosilation stripping. The amine should contain either an ether, hydroxyl or carbonyl functionality, preferably hydroxyl. Preferably, the amine is secondary or tertiary. The amine component should have a boiling point below 220xc2x0 C. at atmospheric pressure, and preferably between 95 and 180xc2x0 C. The amines are less polar than salts and are completely miscible with the polyoxyalkylene-siloxane premix, thus the chance of sedimentation is nonexistent.
The amines useful in this invention include those having the general formula:
NR5tR6uR7v 
R5 is H, an alkyl group of 1 to 8 carbon atoms, an aryl group of 6 to 10 carbon atoms, an alkenyl group of 3 to 8 carbon atoms, t is 0, 1, or 2, R6 is R5, being the same or different, u is 0, 1, or 2, R7 is an alkyl group of 2-10 carbon atoms having hydroxyl, ether or carbonyl functionality, v is 1, and t+u=2. Examples of preferred amines are (N,N-dimethylamino)-2-propanol (DMAP), (N,N-diethylamino)-2-propanol (DEAP), 5-(N,N-diethylamino)-2-pentanol (5DEAP), 2-(N,N-diethylamino) ethanol vinyl ether, Methy 3-(N,N-dimethylamino)propionate, (N,N-dimethylamino)acetone, 2-(N-methylamino)ethanol, 2-(N-propylamino)ethanol, 1-amino-2-propanol, diethylamino-3-butanone, and 2-amino-1-butanol.
The amine component added in accordance with the present invention should comprise about 0.01 to 0.5% by weight of the total reaction charge. The amine also may be combined with the noble metal catalyst, prior to its addition to the siloxane-oxyalkylene polyether admixture.
Hydrosilation
The hydrosilation reaction is conducted in the presence of an effective amount of a noble metal hydrosilation catalyst. Such well-known catalysts include platinum, palladium and rhodium containing complexes. They are reviewed in the compendium, Comprehensive Handbook on Hydrosilation, edited by B. Marciniec and published by Pergamon Press, NY 1992. Chloroplatinic acid and platinum complexes of 1,3-divinyltetramethyldisiloxane particularly are preferred. The catalyst need not be pre-contacted with an olefin prior to its use, but may be added directly to the reaction system. The amine and the catalyst may be pre-contacted and fed to the reaction system together.
The catalyst is employed in an effective amount sufficient to initiate, sustain and complete the hydrosilation. The amount is usually within the range of 1 to 100 parts per million (ppm), based on the total parts of the mixture of reactants.
The amount of polyether added should be at least stoichiometrically equivalent to the amount of organohydrosiloxane, taking into account the number of reactive H sites on the organohydrosiloxane. However, it is customary to employ a stoichiometric excess of polyether, on the order of 110% to 130% of the stoichiometrically equivalent amount, to ensure completeness of the desired hydrosilation reaction, given that some of the polyether may enter into other competitive reactions rather than the hydrosilation of the unsatuated group of the oxyalkylene polyether.
The hydrosilation should be run at 35 to 120 deg C., with the most favorable range being 60 to 110 degree C. A blanket of inert gas is desirable, though not absolutely necessarily, for running the reaction.
Experimental Section
Hydrosilation Procedure
Each hydrosilation was performed in a 4-neck round bottom flask of volume appropriate for the total quantity of the reagents to be used. The flask was fitted with a mechanical stirrer, Friedrich condenser, temperature-controlled heating mantle, thermocouple and sparge tube connected to a nitrogen source. Typically, weighed quantities of a silanic fluid, polyether and amine were added to the flask and the mixture was stirred while being heated to 65-90xc2x0 C. The reaction was catalyzed with 0.03-0.25 ml of 10 mg/ml platinum solution of hexachloroplatinic acid (CPA) in ethanol. A temperature increase indicative of the exothermicity of the hydrosilation was observed after some time, and the reaction mixture cleared to a very pale yellow color. Completeness of the hydrosilation was determined by the test for SiH functional groups. The volume of hydrogen gas produced when a known weight of the reaction mixture was treated with alcoholic potassium hydroxide was measured as described in A. L. Smith (Editor), Analysis of Silicones, John Wiley and Sons, New York 1974, pp 145-149. Reactions that utilized toluene solvent were treated for acetal removal, whereby 1.25 wt % of 1.0N hydrochloric acid was added followed by neutralization with excess sodium bicarbonate and filtration, prior to recovery of the copolymer.
Test Procedures
The following test procedures were utilized in the evaluation of the copolymers produced in the following examples.
Cloud Point
Cloud point is the measurement of water solubility and as used herein, is the temperature at which a siloxane-oxyalkylene copolymer, for example, begins to precipitate out of a 1% aqueous solution. High cloud points are indicative of good water solubility. Cloud points were determined as follows: A 1 gram sample of the copolymer was placed in a 150 ml beaker and dissolved in 99 grams of distilled water. A 1-inch TEFLON(copyright) coated magnetic stirring bar was placed in the beaker, which was placed on a combination stirrer/hot plate. A thermometer was suspended in the solution, with the bulb approximately half an inch (1.27 cm) above the bottom of the beaker. The contents of the beaker were heated at approximately 2 degrees Celsius per minute, while being stirred. The temperature at which the bulb of the thermometer was no longer visible, due to the opacity of the solution, was recorded as the cloud point.
Color
The color of the copolymer was compared to varnish color disk 620C-40 in a Hollge Daylight Comparator. The closest matched color was recorded in GVS.
Viscosity
Viscosity was determined at 25xc2x0 C. using a calibrated Oswald viscometer, which gives an efflux time of approximately 100 seconds. The resulting viscosity is derived from the product of the efflux time in seconds and the specific calibration factor of the viscometer.
Water Solubility
Hach Number
Hach number is a measurement of the water solubility and is herein as a measurement of the clarity of a 5% aqueous solution of the copolymer. For purpose of solubility, the lower the hach number the greater the solubility of the copolymer. The clarity or haze is measured in hach number and was determined by the use of a HACH Turbidimeter, model 2100A, and is reported in Nephelometric Turbidity Units (NTU). Hach numbers less than 20 NTU denote a clear solution.